A photocatalyst made of titania (TiO2) as the principal component having an excellent decomposition effect and hydrophilia performance has been conventionally used in many fields.
The aforementioned decomposition of the titania is made in such a way that electrons and positive holes are generated on a titanium surface by irradiating ultraviolet light contained in sunlight or a fluorescent lamp on the titanium, and the electrons reduce oxygen in air, thereby changing the oxygen into superoxide ions (O2−) and the positive holes oxidize water components adhered to the titanium surface, thereby changing the water components into hydroxyl radicals (OH), and these superoxide ions and hydroxyl radicals oxidize and decompose organic compounds such as contaminants on the titania surface.
As a method of thus forming a titania layer having a decomposition effect and hydrophilia, there is, as shown in Japanese Patent KOKAI (LOPI) No. 12-61314 (page 3 to page 5), a method of forming a titania layer on a surface of a product to be treated by injecting titanium powder on the surface of the product to be treated by way of a blast method.
Note that Japanese Patent KOKAI (LOPI) No. 12-61314 has disclosed no detailed description of what compressed gas is used to inject the titanium powder, but injection of injection powder by a blast method is generally performed by compressed air.
In addition, with regard to use of other compressed gas rather than the compressed air for injection of injection powder by a blast method, there is a injection method of injection powder, as disclosed in Japanese Patent No. 3379913 (page 1 to page 5), by use of a nitrogen gas generated by liquid nitrogen. This method, however, does not have an object of coating a photocatalyst, but the nitrogen gas is used for the purpose of cooling and nitriding the surface of a work piece.